Aion Graviton Build - Low Tone Control has no effect

[box_maker_1]

Hey Folks -

Any advice would be greatly appreciated. I just finished building an Aion Graviton Pedal, and it *mostly* works!

Powers on, passes signal both dry and wet, but the "Low" tone control doesn't have any effect.  My ears told me so, and then I verified by passing some white noise through it into a frequency analyzer - sure enough, high control goes from steep cut to big boost, low control has no impact.

Per the troubleshooting advice in the manual, I tested various voltages of the IC's and transistors, some are quite a bit off - particularly pins 1,2,3 of IC3 - Could that be the issue?  Any other ideas?

See my values and the "correct" values in ()
1   3.75 (4.63)
2   3.75 (4.51)
3   3.75 (4.51)
4   0 (0)
5   4.24 (4.77)
6   4.56 (4.80)
7   4.56 (4.80)
8   9.12 (9.6)
   
IC2   
1   4.56 (4.81)
2   4.56 (4.81)
3   4.12 (4.75)
4   0 (0)
5   4.19 (4.76)
6   4.56 (4.80)
7   4.56 (4.80)
8   9.12 (9.6)
   
IC3   
1   8.54 (4.81)
2   8.54 (4.81)
3   0.21 (4.75)
4   0 (0)
5   4.54 (4.80)
6   4.56 (4.80)
7   4.56 (4.80)
8   9.12 (9.6)

Q1   
D   9.12 (9.6)
S   Couldn't get reading
G   2.27 (4.36)
   
Q2   
E   0.01 (.01)
B   0.6 (.62)
C   3.89 (4.03)
   
Q3   
E   8.34 (8.69)
B   7.42 (8.04)
C   3.76 (4.54)
   
Q4   
E   3.61 (3.80)
B   2.93 (4.22)
C   9.12 (9.6)

[ElectricDruid]

The schematic shows that IC3A (pins 1,2, and 3) is indeed the op-amp related to the Low tone gyrator, so the fact that those voltages are so far out *is* probably why the low tone isn't working.

https://aionfx.com/app/files/docs/graviton_documentation.pdf

There's only a few parts in that gyrator (R25, R26, C15, C16) so check the soldering on those carefully and make sure there's no blobs or shorts or whatever.

The close-but-not-quite voltages on IC1A are more mysterious, but one thing at a time. That drive stage seems to be working anyway.

[box_maker_1]

Solved!  It was indeed a bad solder joint on R25.

Psyched it was an easy one.

Thanks.

[ElectricDruid]

Good work!